The following only covers the original base release of the game, before the updates.

There are (at least) 4 encryption methods used for the files in Shiren 6.

Some files in the "aa" folder, which contains graphics, audio, and in-game cutscene scripts, can be decrypted using shiren_wanderer_decrypt.bms, researched by Spiritovod.
Most other files in the "aa" folder can be decrypted using a modified version of Hololive (https://github.com/Razmoth/Hololive, edit Decryptor.cs, for the part to edit see: "Hololive source code edit.png"). Researched by idkwhatimsaying. Key: DtUp!43AZH46@*fj768GCM@ajNvEdBEB
There are two files in the "aa" folder that use a different encryption method that still hasn't been documented.
The program AddressablesTools can be used to obtain extra info regarding the files.

The "localize" folder contains the game's text files, they can be decrypted + unpacked with shiren6_unpack_localize_files.py, and encrypted + packed with shiren6_pack_localize_files.py. Researched by idkwhatimsaying, Razmoth, and B.

The "bin" folder contains data for dungeons, monsters, items, and more. Its files use an encryption method that still hasn't been documented.